1. Field of the Invention
The present invention relates to a bumper reinforcement having an open section structure including a front face, an upper face and a lower face.
2. Description of the Related Art
A bumper belonging to the safety parts of an automobile is constructed by a bumper reinforcement as a strength member and a bumper cover as a decoration member. The bumper reinforcement can be divided into one having a closed section structure and another having an open section structure. The bumper reinforcement having the closed section structure is disclosed in JP-A-2000-334530, JP-A-2001-199292, JP-A2001-260773, JP-A-2001-227573, U.S. Pat. No. 5,080,411 and so on. On the other hand, the bumper reinforcement having the open section structure is disclosed in JP-A-09-095189, U.S. Pat. No. 4,492,398, U.S. Pat. No. 4,998,761 and so on.
The bumper reinforcement having the closed section structure is advantageous as the strength member. On the other hand, the bumper reinforcement having the open section structure is advantageous to be manufactured easier with high cost performance. In order to incorporate the superior points of these structures into each other, therefore, improvements have been proposed by attaching an auxiliary reinforcement (e.g., a cover having abridging structure in which leg portions are fixed on an upper face and a lower face and which is spaced from a front face) to the front face of the bumper reinforcement, and shown in Japanese Utility Model Registration No. 2554459, USP No. 2002/0047281, DE199 12 272 A1, JP-A-09-095189, U.S. Pat. No. 4,492,398, U.S. Pat. No. 4,998,761 and so on.
The reason why the bumper reinforcement having the open section structure is inferior in the structural strength is caused by the fact that when the front face of the bumper reinforcement receives an impact, the upper face and the lower face of the bumper reinforcement are vertically opened about their boundaries of the front face thereby to lower the modulus of section of the bumper reinforcement. When the upper face and the lower face of the bumper reinforcement are opened, more specifically, the capacity for absorbing the impact energy is reduced to lower the shock absorbing performance as the bumper reinforcement.
In order that the bumper reinforcement having the open section structure may be worth to high structural strength and shock absorbing performance of the bumper reinforcement having the closed section structure, it is then sufficient to prevent the upper face and the lower face of the bumper reinforcement from being opened when the bumper reinforcement receives an impact. Therefore, investigations have been made to develop a bumper reinforcement having the open section structure, which is enabled to exhibit such high structural strength and shock absorbing performance by preventing the upper face and the lower face of the bumper reinforcement from being opened as are not inferior to the bumper reinforcement having the closed section structure.
Here is a case in which a concave groove is formed in the front face of the bumper reinforcement so as to reinforce the bumper reinforcement. With the concave groove being merely formed, however, the rigidities of the upper face and the lower face of the bumper reinforcement are inferior to that of the front face so that the upper face or the lower face of the bumper reinforcement is easily made to buckle by the impact applied on the front face. This buckling can be avoided by increasing the thickness of the upper face or the lower face. At the same time, however, there are lost the advantages of the light weight and the reduction of the material which are owned by the bumper reinforcement having the open section structure. Therefore, the inventors of the invention have investigated to develop the bumper reinforcement having the open section structure, which is enabled to exhibit the aforementioned high structural strength and shock absorbing performance more sufficiently by preventing the buckling of the upper face and the lower face of the bumper reinforcement.
First of all, with a view to preventing the upper face and the lower face of the bumper reinforcement from being opened, the present invention has developed a bumper reinforcement comprising an outer reinforcement and an inner reinforcement housed in the outer reinforcement. The outer reinforcement is made of a channel member of an open section having a front face, an upper face and a lower face, and the inner reinforcement is made of an angle member having a vertically pair of skirt plate portions folded from an intermediate portion. And, the intermediate portion of the inner reinforcement is joined to the front face of the outer reinforcement. The upper skirt plate portions of the inner reinforcement are joined at their end portions to the upper face of the outer reinforcement, and the lower skirt plate portions are joined at their end portions to the lower face of the outer reinforcement.
The following examples can be enumerated as the preferable sectional shapes of an inner reinforcement. At the individual skirt plate portions of the inner reinforcement, more specifically, there are formed the top portions which are protruded toward the front face of the outer reinforcement to divide the upper and lower skirt plate portions are further divided into the inner skirt plate portions and the outer skirt plate portions. Then, the intermediate portion of the inner reinforcement corresponds to the portion composed of the confronting end portions of the inner skirt plate portions, and the remaining end portions of the individual inner skirt plate portions protrude as the top portions formed with the end portions of the outer skirt plate portions, toward the front face of the outer reinforcement. The outer contact face portion of the inner reinforcement, that is the remaining end portion of the aforementioned outer skirt plate portion, is joined individually to the upper face and the lower face of the outer reinforcement thereby to follow the sectional shape of the inner reinforcement.
The outer reinforcement is usually formed from a single metal plate by a roll-forming method. Unlike the auxiliary reinforcement attached to the front face of the outer reinforcement, the inner reinforcement is mounted in an inside of the outer reinforcement formed by the front face, the upper face and the lower face. The inner reinforcement can be classified into a separate type, in which the inner reinforcement divided into a pair of the vertically symmetrical members is individually provided with the inside of the front face, and the upper/lower faces of the outer reinforcement, and a single formed type, in which the inner reinforcement is integrally formed to be provided continuously with the inside of the lower face, the front face, and the upper face of the outer reinforcement.
The inner reinforcement of either type has a common structure, in which the outer contact face portions are directly joined to the upper/lower faces of the outer reinforcement through the intermediate portion joined to the front face of the outer reinforcement. When an impact applied to the front face of the outer reinforcement, therefore, the end portions of the individual skirt plate portions forming the intermediate portion of the inner reinforcement joined to the front face of the outer reinforcement, and the end portions of the skirt plate portions of the inner reinforcement forming the outer contact face portions joined individually to the upper/lower faces of the outer reinforcement, are retracted relative to the intermediate portion of the skirt plate portion so that the skirt plates are folded around the center portions of the skirt plate portions. This folding structure inclines the entire skirt plate portions inwardly when an impact applied, so that the upper face and the lower face of the outer reinforcement can be prevented from being opened.
The intermediate portions of the individual skirt plate portions of the inner reinforcement are the top portions which are formed at the boundary between the inner skirt plate portions and the outer skirt plate portions and which are protruded toward the front face of the outer reinforcement. In this case, when an impact applied to the front face of the outer reinforcement, the end portions of the upper and the lower inner skirt plate portions joined to the front face and the other end portions of the upper and the lower outer skirt plate portions joined to the upper/lower faces of the outer reinforcement individually are retracted from the top portions so that the inner skirt plate portions and the outer skirt plate portions are folded around the top portions thereby to incline the entire skirt plate portions inward. As a result, it prevents the upper face and the lower face of the outer reinforcement from being opened.
The outer reinforcement has to retain the space at its inside for allowing the top portions of the inner reinforcement to protrude. In case the front face of the outer reinforcement is flat, therefore, the intermediate portion of the inner reinforcement is protruded toward and joined to the front face of the outer reinforcement. In case the impact is applied from the front to the reinforcement having that structure, however, the top portions may obstruct such a displacement of the skirt plate portions, as follows the displacement of the front face of the outer reinforcement. Therefore, it is advisable to form the concave groove portion extending in the extending direction of the outer reinforcement, in the front face of the outer reinforcement. It is also advisable to join the intermediate portion of the inner reinforcement to the concave groove portion of the outer reinforcement and the outer contact face portions of the inner reinforcement individually to the upper face and the lower face of the outer reinforcement. It is preferable that the outer reinforcement has the concave groove portion formed in the front face and extending in the extending direction of the outer reinforcement, that the intermediate portion of the inner reinforcement is joined in face-to-face contact to the bottom face of the concave groove portion, and that the outer contact face portions of the inner reinforcement are joined individually to the upper face and the lower face of the outer reinforcement.
When the bottom face of the concave groove portion of the outer reinforcement is positioned backward to an extent corresponding to the protrusion of the top portions of the inner reinforcement with respect to the front face, the skirt plate portions of the inner reinforcement or the end portions of the inner skirt plate portions can be joined as they are to the bottom face or the side faces of the groove portion of the outer reinforcement. In case the impact is applied to the reinforcement, therefore, the top portions of the inner reinforcement does not obstruct the displacement of the skirt plate portions, as follows the displacement of the front face of the outer reinforcement. Moreover, the concave groove portion of the outer reinforcement enhances the rigidity of the front face to restrain even the partial deformation occurred. In case the bumper reinforcement receives a partial impact, as exemplified by a pole collision or the like, the front face is deformed over a wide range in the extending direction of the outer reinforcement, thereby to prevent the partial deformation of the front face, that is, to prevent the deterioration of the shock absorbing performance of the bumper reinforcement due to the buckling.
In order to guide the folding of the inner skirt plate portions and the outer skirt plate portions of the inner reinforcement in case the concave groove portion is formed in the outer reinforcement, it is advisable to make the inner skirt plates shorter, or the outer skirt plates longer, thereby to bring the rising angle of the inner skirt plates from the end portions to the top portions of the skirt plate portions of the inner reinforcement, closer to the inclination angle of the side faces of the concave groove portion of the outer reinforcement.
The inner skirt plate portions and the outer skirt plate portions of the inner reinforcement are folded by retracting the end portions of the inner skirt plates and the outer skirt plates from the top portions, as has been described hereinbefore. If the top portions of the inner reinforcement are positioned far from the side faces of the concave groove portion of the outer reinforcement, the inner skirt plate portions of the inner reinforcement become reluctant to receive the influences of the retractions of the concave groove portion of the outer reinforcement. As a result, the moment of the outer skirt plate portions of the inner reinforcement to be inclined inward is reduced the actions to restrain the openings of the upper face and the lower face of the outer reinforcement. It is, therefore, desirable that the top portions of the inner reinforcement are positioned as close to the side faces of the concave groove portion as possible.
In the same time, the inner skirt plate portions of the inner reinforcement are closer to the side faces but not in close contact with the side faces of the concave groove portion of the outer reinforcement. It is advisable that the rising angle of the inner skirt plate portions of the inner reinforcement from the end portions joined to the bottom face of the concave groove portion of the outer reinforcement is close to the inclination angle of the side faces of the concave groove portion of the outer reinforcement. That is, provided an open angle relation of the inner skirt plate portions against the side faces. It is advisable that a specific rising angle of the inner skirt plate portions forms a space for allowing the inclination of the inner skirt plate portions with respect to the side faces of the concave groove portion of the outer reinforcement when the inner skirt plate portions and the outer skirt plate portions are folded from the top portions. The space between the inner skirt plate portions of the inner reinforcement and the side faces of the concave groove portion of the outer reinforcement provides an inclination margin for the inner skirt plate portions of the inner reinforcement thereby to allow the inclination of the inner skirt plates.
The inner reinforcement may be of the separate type, as described hereinbefore. However, this construction raises the problems: an increase in the number of parts; the difficulty for positioning the inner reinforcement when joined to the outer reinforcement; and the vertically uneven retractions, as received by the upper and lower inner reinforcements, of the front face or the concave groove portion of the outer reinforcement. With a view to restraining the increase in the parts number or receiving the retraction of the front face or the concave groove portion of the outer reinforcement vertically equally, therefore, the construction is made such that the inner reinforcement is a single formed member having the intermediate portion and such that the bottom face of the concave groove portion of the outer reinforcement and the intermediate portion of the inner reinforcement are joined in face-to-face contact to each other.
Here, it is desirable that the individual top portions are formed at vertically symmetric positions so that the upper and lower inner skirt plate portions and the upper and lower outer skirt plate portions of the inner reinforcement may be likewise folded vertically homogeneously by the retraction of the concave groove portion of the outer reinforcement. In order to receive the influences of the retraction of the concave groove portion of the outer reinforcement sufficiently, moreover, it is preferable, in this integral type inner reinforcement, to make the inner skirt plates shorter, or the outer skirt plates longer, thereby to bring the rising angle of the inner skirt plates from the end portions to the top portions of the skirt plate portions of the inner reinforcement, closer to the inclination angle of the side faces of the concave groove portion of the outer reinforcement. At this time, the inner skirt plate portions of the inner reinforcement are closer to the side faces but not in close contact with the side faces of the concave groove portion of the outer reinforcement.
In order to prevent the buckling of the upper face or the lower face of the outer reinforcement, the concave groove portion extending in the extending direction of the outer reinforcement is formed in the front face, and ribs extending in the extending direction of the outer reinforcement are also formed individually in the upper face and the lower face. As a result, the upper face and the lower face of the outer reinforcement can be parted by the ribs into the front side face portions and the rear side face portions. By installing the outer contact face portions of the inner reinforcement to the individual ribs of the outer reinforcement, the outer contacting face portions are joined to the upper face and the lower face of the outer reinforcement, and the intermediate portion of the inner reinforcement is joined to the front face of the outer reinforcement. Thus, it has solved the problem of the buckling in the upper face or the lower face of the outer reinforcement.
The outer contact face portions of the inner reinforcement may be joined to any of the front side face portions, the ribs, or the rear side face portions in the upper/lower faces of the outer reinforcement. However, the individual join positions are desirably located such that the line connecting the individual join positions is in parallel to the line connecting the two corners formed between the upper/lower faces and the front face.
The ribs have a function to disperse the impact applied to the front face of the outer reinforcement in the extending direction of the ribs, i.e., in the extending direction of the bumper reinforcement, thereby providing the rigidity to the upper/lower faces sufficiently compared to that of the front face having the concave groove portion. As a result, it restrains or prevents the buckling of the upper face and the lower face of the outer reinforcement.
The ribs also have a function to disperse the impact, as transmitted individually to the upper/lower faces of the outer reinforcement, in the extending direction of the outer reinforcement. If the impact dispersing action is effective at different timings on the upper face and the lower face, the load is maldistributed to the face having slower timing, thereby to cause the buckling. Therefore, it becomes the basis that a pair of ribs are provided at identical positions from the corners between the upper/lower faces and the front face thereby to give an equal width to the paired front side face portions of the upper/lower faces of the outer reinforcement.
Here, the phrase xe2x80x9cidentical positionsxe2x80x9d means that, in the sectional configuration of the outer reinforcement, the ribs formed individually in the upper face and the lower face are located at the same positions, as taken in the vehicle frame direction, from the corners between the upper/lower faces and the front face of the outer reinforcement. Usually, in the sectional configuration of the outer reinforcement, the upper face and the lower face take the equal lengths in the vehicle frame direction and are parallel. Therefore, the ribs take axially symmetric positions across the center line (usually a bisector of the front face) between the upper face and the lower face so that the paired front side face portions and the paired rear side face portions, as divided by the ribs, of the upper face and the lower face of the outer reinforcement have equal lengths in the depth direction.
By the front side face portions and the rear side face portions classified by the ribs, the upper/lower faces of the outer reinforcement are divided into lengths in the depth direction shorter than the upper/lower faces having no rib, thereby to occur buckling hardly. If the ribs are arranged at deep positions in the depth direction, i.e., at positions close to the back face of the reinforcement, however, the depth of the front side face portions is enlarged to increase the apprehension of the buckling of the front side face portions. On the contrary, if the ribs are arranged at shallow positions in the depth direction, i.e., at positions close to the front face of the reinforcement, the depth of the rear side face portions is enlarged to increase the apprehension of the buckling of the rear side face portions. Therefore, it is advisable that the ribs are formed in one pair on a normal, as passing through the center of gravity of the reinforcement, to the upper face and the lower face. In this case, the individual ribs are positioned on the common normal so that they never fail to take the axial symmetry.
As a result, the front side face portions and the rear side face portions of the upper/lower faces of the outer reinforcement take dynamically equivalent relations (in which the load is applied substantially equivalently) across the normal passing through the center of gravity of the reinforcement. Therefore, it is possible to minimize the apprehension that the load is maldistributed to the front side face portions or the rear side face portions and causes to occur buckling.
The specific shapes of the ribs are exemplified by step portions dividing the front side face portions and the rear side face portions into two steps, or a convex bar or concave groove capable of arranging the front side face portions and the rear side face portions in a common plane. The steps can also be exemplified by steps to make the distance of the paired front side face portions of the upper/lower faces relatively narrower than that of the paired rear side face portions of the upper/lower faces. On the contrary, narrow steps are exemplified to make the distance of the paired front side face portions of the upper/lower faces relatively wider than that of the paired rear side faces portions of the upper/lower faces.
Moreover, the convex bar, as one of the specific shapes of the ribs, is exemplified by a side convex bar having a face wider than those of the front side face portions and the rear side face portions of the upper/lower faces of the outer reinforcement. On the other hand, the concave groove is exemplified by side concave grooves having a face relatively narrower than those of the front side face portions and the rear side face portions of the upper/lower faces of the outer reinforcement.
The side convex bars or the side concave grooves can be obtained by the construction, in which the steps and the narrow steps mentioned above can be formed continuously in a set, so that intermediate face portions are formed between the front side face portions and the rear side face portions formed. As a result, the individual lengths of the front side face portions and the rear side face portions are shortened in the depth direction by the length of the intermediate face portions, thereby to make buckling harder. The front side face portions and the rear side face portions divided by the side convex bars or the side concave grooves may be arranged in a common plane or at two steps shifted.
In addition, the steps, the side convex bars, and the side concave grooves to form the ribs are active to bring the leg portions of the auxiliary reinforcement, as attached to the front face of the outer reinforcement, into abutment against the upper face and the lower face of the outer reinforcement thereby to position the auxiliary reinforcement with respect to the outer reinforcement. Moreover, the steps, the side convex bars, and the side concave grooves to form the ribs are also active to position the inner reinforcement with respect to the outer reinforcement when the outer contact face portions of the inner reinforcement having the top portions are joined to the inner sides of the upper face and the lower face of the outer reinforcement.